The present invention relates generally to compositions of purified natural beta-carotenes and methods for their purification from plants. More particularly, the beta-carotene preparations are enriched in the 9-cis isomer compared to the all-trans isomer. The purified beta-carotenes are useful as dietary vitamin A supplementation, as pharmaceuticals and, particularly preparations containing high purity 9-cis beta-carotene, as anti-oxidants in a variety of therapeutic and preventative applications.
The carotenes are chemical precursors of vitamin A. Vitamin A, which is synthesized from carotenes, is essential to a wide variety of physiologic processes in animals, including humans. For example, vitamin A is important in visual sensitivity, and deficiencies of vitamin A may lead to lack of night vision or even blindness. Vitamin A is also necessary to the proper functioning of epithelial tissues.
The carotenes are composed of several forms, including alpha-, beta- and gamma-carotenes. Of these, the beta-carotene isomers have the most vitamin A activity and are the most prevalent in nature, being found in dark green leafy vegetables, yellow and orange vegetables and fruits, and in algae. The concentration of beta-carotene in the edible plants is relatively low and large quantities must be consumed, or else the beta carotene must be supplied as a dietary supplement.
More recently, beta-carotene has been reported to prevent or reduce the risk of heart disease and stroke and certain types of cancers, such as cancer of the breast, lung, colon, prostate, and cervix.
To meet the growing commercial markets in health and coloring industries, a number of methods have been proposed to purify the beta-carotenes. Few procedures, if any, however, have successfully overcome the considerable obstacles posed by the need to prepare compounds of high purity from natural sources in an economical manner while maintaining acceptability to the consumer and regulatory agencies. For example, U.S. Pat. No. 4,439,629 to Riiegg describes treating algae with calcium hydroxide at an elevated temperature to saponify the chlorophyll and produce a residue which is then filtered, dried, and extracted with a solvent, such as a halogenated hydrocarbon or an aliphatic or aromatic hydrocarbon, and recrystallized to yield enriched all-trans beta carotene.
U.S Pat. No. 5,019,668 to Keat et al., describes the recovery of carotenoids from palm oil by an esterification process using an edible oil and subjecting the mixture to vacuum distillation at a substantially elevated temperature. The concentration of beta-carotene in these preparations was described as being up to about 1.9%.
U.S. Pat. No. 4,680,314 to Nomura et al. describes a process for concentrating algae and extracting beta-carotene with an edible oil such as vegetable oil at elevated temperatures, i.e., 66.degree.-100.degree. C. The concentration of carotene in the oil extract was reported to be on the order of 1.9%. U.S. Pat. No. 4,713,398, also to Nomura et al., describes compositions of carotene prepared from algae at concentrations of 0.5% to 7.5% by weight of an edible-oil medium.
Beta-carotene has been prepared by chemical synthesis, but results in the production of only the all-trans form and very little of the cis-isomers of beta-carotene.
There remains a significant need in the art for a method of producing natural beta-carotene compositions of high purity, particularly compositions which are enriched in the 9-cis isomer of beta carotene. The method desirably will provide beta-carotene in a form which maintains its anti-oxidant capability, and in a form which is acceptable to food and health regulatory agencies and to consumers. Moreover, the methods should provide the ability to produce the beta-carotene containing compositions on a large scale and in an economically feasible manner. Quite surprisingly, the present invention fulfills these and other related needs.